// GZipOutputStream.cs
//
// Copyright (C) 2001 Mike Krueger
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
// 
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module.  An independent module is a module which is not derived from
// or based on this library.  If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so.  If you do not wish to do so, delete this
// exception statement from your version.

using System;
using System.IO;
using ICSharpCode.SharpZipLib.GZip;
using ICSharpCode.SharpZipLib.Silverlight.Checksums;
using ICSharpCode.SharpZipLib.Silverlight.Zip.Compression;
using ICSharpCode.SharpZipLib.Silverlight.Zip.Compression.Streams;

namespace ICSharpCode.SharpZipLib.Silverlight.GZip
{
    /// <summary>
    /// This filter stream is used to compress a stream into a "GZIP" stream.
    /// The "GZIP" format is described in RFC 1952.
    ///
    /// author of the original java version : John Leuner
    /// </summary>
    /// <example> This sample shows how to gzip a file
    /// <code>
    /// using System;
    /// using System.IO;
    /// 
    /// using ICSharpCode.SharpZipLib.GZip;
    /// using ICSharpCode.SharpZipLib.Core;
    /// 
    /// class MainClass
    /// {
    /// 	public static void Main(string[] args)
    /// 	{
    /// 			using (Stream s = new GZipOutputStream(File.Create(args[0] + ".gz")))
    /// 			using (FileStream fs = File.OpenRead(args[0])) {
    /// 				byte[] writeData = new byte[4096];
    /// 				Streamutils.Copy(s, fs, writeData);
    /// 			}
    /// 		}
    /// 	}
    /// }	
    /// </code>
    /// </example>
    public class GZipOutputStream : DeflaterOutputStream
    {
        #region Instance Fields

        /// <summary>
        /// CRC-32 value for uncompressed data
        /// </summary>
        protected Crc32 crc = new Crc32();

        private bool headerWritten_;

        #endregion

        #region Constructors

        /// <summary>
        /// Creates a GzipOutputStream with the default buffer size
        /// </summary>
        /// <param name="baseOutputStream">
        /// The stream to read data (to be compressed) from
        /// </param>
        public GZipOutputStream(Stream baseOutputStream) : this(baseOutputStream, 4096)
        {
        }

        /// <summary>
        /// Creates a GZipOutputStream with the specified buffer size
        /// </summary>
        /// <param name="baseOutputStream">
        /// The stream to read data (to be compressed) from
        /// </param>
        /// <param name="size">
        /// Size of the buffer to use
        /// </param>
        public GZipOutputStream(Stream baseOutputStream, int size)
            : base(baseOutputStream, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size)
        {
        }

        #endregion

        #region Public API

        /// <summary>
        /// Sets the active compression level (1-9).  The new level will be activated
        /// immediately.
        /// </summary>
        /// <param name="level">The compression level to set.</param>
        /// <exception cref="ArgumentOutOfRangeException">
        /// Level specified is not supported.
        /// </exception>
        /// <see cref="Deflater"/>
        public void SetLevel(int level)
        {
            if (level < Deflater.BEST_SPEED)
            {
                throw new ArgumentOutOfRangeException("level");
            }
            deflater_.SetLevel(level);
        }

        /// <summary>
        /// Get the current compression level.
        /// </summary>
        /// <returns>The current compression level.</returns>
        public int GetLevel()
        {
            return deflater_.GetLevel();
        }

        #endregion

        #region Stream overrides

        /// <summary>
        /// Write given buffer to output updating crc
        /// </summary>
        /// <param name="buffer">Buffer to write</param>
        /// <param name="offset">Offset of first byte in buf to write</param>
        /// <param name="count">Number of bytes to write</param>
        public override void Write(byte[] buffer, int offset, int count)
        {
            if (! headerWritten_)
            {
                WriteHeader();
            }

            crc.Update(buffer, offset, count);
            base.Write(buffer, offset, count);
        }

        /// <summary>
        /// Writes remaining compressed output data to the output stream
        /// and closes it.
        /// </summary>
        public override void Close()
        {
            try
            {
                Finish();
            }
            finally
            {
                if (IsStreamOwner)
                {
                    baseOutputStream_.Close();
                }
            }
        }

        #endregion

        #region DeflaterOutputStream overrides

        /// <summary>
        /// Finish compression and write any footer information required to stream
        /// </summary>
        public override void Finish()
        {
            // If no data has been written a header should be added.
            if (!headerWritten_)
            {
                WriteHeader();
            }

            base.Finish();

            var totalin = deflater_.TotalIn;
            var crcval = (int) (crc.Value & 0xffffffff);

            byte[] gzipFooter = {
                                    (byte) crcval, (byte) (crcval >> 8),
                                    (byte) (crcval >> 16), (byte) (crcval >> 24),
                                    (byte) totalin, (byte) (totalin >> 8),
                                    (byte) (totalin >> 16), (byte) (totalin >> 24)
                                };

            baseOutputStream_.Write(gzipFooter, 0, gzipFooter.Length);
        }

        #endregion

        #region Support Routines

        private void WriteHeader()
        {
            if (!headerWritten_)
            {
                headerWritten_ = true;
                var mod_time = (int) ((DateTime.Now.Ticks - new DateTime(1970, 1, 1).Ticks)/10000000L);
                    // Ticks give back 100ns intervals
                byte[] gzipHeader = {
                                        // The two magic bytes
                                        (GZipConstants.GZIP_MAGIC >> 8), (GZipConstants.GZIP_MAGIC & 0xff),
                                        // The compression type
                                        Deflater.DEFLATED,
                                        // The flags (not set)
                                        0,
                                        // The modification time
                                        (byte) mod_time, (byte) (mod_time >> 8),
                                        (byte) (mod_time >> 16), (byte) (mod_time >> 24),
                                        // The extra flags
                                        0,
                                        // The OS type (unknown)
                                        255
                                    };
                baseOutputStream_.Write(gzipHeader, 0, gzipHeader.Length);
            }
        }

        #endregion
    }
}